Textile operations often require simultaneously handling of many continuous linear elements, such as yarns or strands, to produce a product. Examples of such operations are roving and beaming. And the quality of the product depends upon the ability of apparatus to keep a positive end count of the linear elements being processed. So apparatus cannot be allowed to blithely operate without monitoring the movement of the linear elements during processing.
It has been a practice to produce a composite roving by withdrawing strands or rovings from packages held in creels and converging the strands or rovings into a group and winding the group on a rotatable packaging tube, collet or collector. It has been found that one of the major problems in producing such a composite linear product lies in maintaining a positive end count of the number of strands or rovings being combined. The specifications for different products vary, but there has been an increased requirement for accuracy in maintaining a predetermined number or minimum number of rovings or strands in the composite product. Thus, a need has developed for increased reliability and durability in control to meet specifications for a composite roving with a positive end count.
Apparatus has been used that performed an end count function as an incidental control in effecting a required tension on each strand to provide a composite roving made up of individual rovings having a substantially uniform tension. In U.S. Pat. No. 3,361,375 issued Jan. 2, 1968, an end count was provided by a drop member or drop wire held in elevated position by the tension of the roving threaded through a guide eye in the drop member. When the roving broke, the member normally fell to close a switch that effected interruption in the operation of a winding motor and a feed roll motor. While the above described approach was satisfactory for use in the device as described, difficulties were encountered. The apparatus as a whole was primarily a tension sensing and tension controlling device. Thus, if a tension controlling portion of the apparatus failed, it was possible to obtain a breakout signal although no strand was broken. Further, abrasion on the strand or roving may mechanically reduce the strength of the strand or roving and may further interfere with the functioning of the tensioning devices. In addition, breakage of the strand or roving at certain points of the apparatus may not be detected by the device since the licking or wrap around capabilities of a filament or strand may effect sufficient tension in the area of the drop wire or member supported by the strand to maintain support of the drop wire detecting member even though the strand is broken.
Other devices for handling linear elements have recently been developed. For example, one such device has a motion detection means that includes: a movably mounted guide member upon which the linear element is turned during advancement; and an electrical circuit effective to supply the intermittent electrical motion signals in response to the sense motion of the linear material during its advancement. The electrical circuit includes an electrical switch comprising a fixed electrical contact and an electrical conductor carried by and moving with the movable guide member. The electrical conductor intermittently contacts the fixed electrical contact during advancement of the linear element over the movable guide member.
Further, apparatus has been used that performs an end count function by providing a motion signal changing in magnitude with changes in the motion of the linear elements and control circuit responsive to the magnitude of the motion signals. For example, tachometer generators and piezoelectric crystals have been used. But these prior devices tend to be too frail and expensive for production use.
Improved controls have been needed.